SAN SALVADOR, EL SALVADOR: A strong earthquake hit off the coast of El Salvador early Thursday, sending frightened residents running out of their homes in the predawn hours. Authorities say a tsunami is possible.

The US Geological Survey reported the quake had a preliminary magnitude of 6.6. Its epicentre was about 17 miles (28 kilometres) south-southeast of La Libertad, a suburb of the regional capital, Santa Tecla, and it was recorded at a depth of 65 kilometres (40 miles).

Via Twitter, El Salvador's Ministry of Environment and Natural Resources warned of a possible tsunami and advised people to stay away from the Pacific Ocean for the next four hours.

The earthquake was felt strongly in the capital, San Salvador. People left their homes with flashlights, and power was knocked out in at least some areas.